The stars of NBC’s “Grimm” were put through an acting exercise while filming “Beeware,” the latest episode debuting at 8 p.m. Nov. 11.

In the episode, Nick (David Giuntoli) and Hank (Russell Hornsby) are called to a case where a flash mob results in a homicide involving a swarm of bees.

When fans watch the episode Friday, they’ll see the bees. Giuntoli, Hornsby and their co-stars did not while filming.

“It was just bizarre acting with bees that weren’t there,” Giuntoli told me recently. “You look ridiculous on set, responding to a swarm of bees.”

Giuntoli was used to acting in scenes in which his partner isn’t there. For a scene in the pilot where someone morphed from human to demon, for example, he acted opposite “a stick with an X on it.” The bee scenes were a lot different, he said.

“Our directors have to shout from behind the camera, like, ‘There’s one bee! Now there’s five! Now there’s 10! Where are they coming from? Are they at the windows? Well what happened?’

“I’ve seen the footage and it’s just a ridiculous enterprise.”

Watch three previews of the episode in the video player at the top of the post. Here’s NBC’s description of the episode:

The station is abuzz as Nick (David Giuntoli) and Hank (Russell Hornsby) are called to a case where an innocent flash mob results in a gruesome homicide. As Nick delves further into the investigation, he learns more about his unique family history, and finds himself at odds when he and Hank are assigned to protect a dark character from his recent past. Bitsie Tulloch, Silas Weir Mitchell, Sasha Roiz and Reggie Lee also star.